add-tab

Adds a tab to a tab-control at a specified position and displaying a
specified label.

tab-control is the existing tab-control widget to which the tab
will be added.

tab-info-or-name is either an existing tab-info instance or a
symbol to name a new tab. If a symbol, a new instance of the tab-info class having
that name will be automatically created. If a tab-info instance, it may be an
instance either of the tab-info class itself or of an
application-defined subclass of tab-info.

label is a string to display on the tab. If
tab-info-or-name is a tab-info object that already has a
label property,
then nil may be passed here to use the
existing label.

index indicates the position at which to add the
new tab. Zero will place the new tab at the leftmost position, 1 at
the next leftmost position, and so on. A negative number indicates a
position from the right end of the existing tabs, where -1 is the last
(rightmost) position, -2 the next rightmost position, and so on. The
default is -1 to add the new tab to the right of all of the existing
tabs.